SiN Resurrected is the name of the Mod, it changes the singleplayer campaign of SiN by tweaking the weapons, items and enemies.
Here is a brief list of some things the Mod does:
Changes the main menu and "X-files screen" typewriter sound with a more pleasant one
Changes the sound played when the player finds a secret
Fixes the wrong text that showed when the player completed a objective in later levels
Adds the nude Elexis skin for multiplayer
Adds some items throughout the levels
Rebalances the Pulse cannon
Expands some of the dialogs and makes them clarify the storyline better
Adds secondary objectives to some of the later levels to increase replay ability of the game
Adds a number of action-based outcomes to some levels to increase interactivity of the game
FINALLY fixes the Biomass to Area 57 bug, so now the player can continue the game normally